Get rid of a lot of () for getters.

lib/html/src/CustomEventWrappingImplementation.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class CustomEventWrappingImplementation extends EventWrappingImplementation implements CustomEvent {
   CustomEventWrappingImplementation._wrap(ptr) : super._wrap(ptr);
 
   factory CustomEventWrappingImplementation(String type,
       [bool canBubble = true, bool cancelable = true, Object detail = null]) {
     final e = dom.document.createEvent("CustomEvent");
     e.initCustomEvent(type, canBubble, cancelable, detail);
     return LevelDom.wrapCustomEvent(e);
   }
 
-  String get detail() => _ptr.detail;
+  String get detail => _ptr.detail;
 }